Effect of thiourea on the copper cathode polarization behavior in acidic copper sulfate at 65 degrees C

The effects of different concentrations of thiourea (TU) on the copper cath ode polarization behavior in an acidic copper sulfate solution was investig ated at 65 degreesC using potentiodynamic and galvanostatic methods. The re sults showed that there was a transition current density for each concentra tion of the fresh TU, below which the TU exhibited a polarizing effect and above which the TU manifested a depolarizing effect on the copper cathode. The depolarizing effect increased with cathodic overpotential. The transiti on current density increased with TU concentration and decreased with time. Lowering of the electrolyte temperature resulted in diminution of the tran sition current density considerably. In the modern copper electrorefining c onditions (65 degreesC, 150 to 350 A/m(2), and using approximately 1 to 4 m g/dm(3) of TU), TU produces only a polarizing effect on the copper cathode.